The exemplary embodiment relates to enforcing policies over links (references) across markup language documents. It finds particular application in connection with Extensible Markup Language (XML) documents, and will be described with particular reference thereto.
XML is a widely used markup language which aids information systems in sharing structured data, encoding documents, and serializing data. An XML document may have many links (e.g., uniform resource locators (URLs)) within the document that express the relationship of the document to other resources, which may also be XML documents. Although the links inside the document are precisely defined through their syntactic and semantic structure, it is difficult and time-consuming to gather information about the context in which the links are used and how links to multiple documents interrelate.
XML schemas can enforce properties within a particular document by, for example, enforcing a certain format for links, but schemas are not designed to enforce complex (or even basic) relationships between linked documents.
Enforcing rules across a large number of resources which refer to each other can be challenging and computationally intensive. Resources may be primarily XML resources referring to other XML or non-XML resources using the URL mechanism. A convenient mechanism to ensure that certain properties hold over the whole set of inter-related XML resources is desirable.
Currently, there are tools which perform semantic reasoning across objects having properties. There are also approaches to migrate an XML dataset into an ontological domain for use by a semantic reasoner, but there is no tool to apply a semantic reasoner to resource relationships such as links between XML documents.
For example, ontology-based policy management has recently been proposed which relies on the Web Ontology Language (OWL), the ontology language proposed by the W3C (see W3C. 2009-10-27. http://www.w3.org/TR/owl2-overview/), which is a family of knowledge representation languages for authoring ontologies. The additional use of a Semantic Web Rule Language (SWRL), which is based on a combination of the OWL DL and OWL Lite sublanguages of the OWL Web Ontology Language with the Unary/Binary Datalog RuleML sublanguages of the Rule Markup Language (see http://www.w3.org/Submission/SWRL/), has been proposed, so as to express additional rules using Horn-like clauses.
The present exemplary embodiment provides a system to create a resource ontology for a set of linked resources based on the nature of the resources and the nature of the links between them. It further provides a system which can verify that a policy holds (is valid) across the set of resources and links by automated semantic reasoning.